Heat-Sensitive Layer for Lithium Ion Battery Thermal Safety
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Solution Overview
Problem
Existing heat-sensitive layers for lithium ion secondary batteries are inefficient in blocking rising temperatures during abnormal heating, often requiring additional components and complex manufacturing processes, which can lead to increased internal resistance and reduced battery performance.
Innovation Solution
A heat-sensitive layer composition comprising particles with a polyolefin first component and an acrylic polymer second component, where the second component is partially exposed, providing a storage modulus of 10 kPa or more at 60°C and 1 kPa or less at 150°C, effectively increasing internal resistance and reducing current during abnormal heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermally expansive microcapsules are used to inhibit temperature rise during abnormal heating, then temperature safety is improved, but device complexity increases due to requiring special current collectors or additional binders
Solution Approach 1:
The patent combines the heat-sensitive function and adhesive function into a single layer. The heat-sensitive layer comprises polyolefin particles with adhesive resin, eliminating the need for separate thermally expansive microcapsules and additional binders. This merging resolves the technical contradiction by achieving temperature safety without increasing device complexity.
Solution Approach 2:
The heat-sensitive layer serves multiple functions simultaneously: it provides thermal response (shutdown at melting point), adhesion between electrodes and separator, and mechanical integrity. This multi-functionality eliminates the need for separate components, resolving the contradiction between temperature safety and device complexity.
2Reliability
If separator melts to block micropores at high temperature, then current cutoff function is improved, but harmful effects occur when temperature exceeds melting point causing rapid contraction and short-circuit
Solution Approach 1:
The heat-sensitive layer uses composite polyolefin particles with adhesive resin, creating a material that maintains structural integrity at high temperatures while providing shutdown function. The composite structure prevents rapid contraction and electrode contact, resolving the contradiction between shutdown function and harmful effects.
Solution Approach 2:
The patent creates a localized heat-sensitive layer with specific properties (polyolefin particles with adhesive resin) positioned between electrodes. This layer provides targeted thermal response and structural support at critical locations, preventing short-circuits while maintaining shutdown function.
3Reliability
If additional components are added to achieve heat-sensitive function, then temperature control is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges heat-sensitive particles and adhesive resin into a single composible mixture that can be applied in one coating step. This eliminates the need for separate application processes for different components, improving ease of manufacture while maintaining temperature control functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed heat-sensitive layer efficiently blocks rising temperatures during abnormal heating by increasing battery internal resistance, thereby reducing current and enhancing battery performance and safety.
Implementation Method 1
the first component is a polyolefin and has a melting point of at least 60°C and not higher than 160°C
Implementation Method 2
the second component is an acrylic polymer and has a glass transition temperature of at least -60°C and not higher than 20°C, and substantially partially disposed at the particle surface
Data Source
AI summary
Provided is a heat-sensitive layer for a lithium ion secondary battery that can efficiently block rising temperature during abnormal heating by increasing battery internal resistance and thereby reducing current. The heat-sensitive layer for a lithium ion secondary battery is formed from a heat-sensitive layer composition containing particles in each of which a second component is substantially partially disposed at the outside of a particle formed from a first component. The heat-sensitive layer composition has a storage modulus at 60°C of 10 kPa or more and a storage modulus at 150°C of 1 kPa or less.